Regulating system for generator driving engines



Nov. 7, 1939.

T. DEEG REGULATING SYSTEM FOR GENERATOR DRIVING ENGIEJES Filed July 12,1938 2 Sheets-Sheet 1 INVENTOR 777600 07 2999.

ATTORNEY T. DEEG Nov. 7 1939.

REGULATING SYSTEM FOR GENERATOR DRIVING ENGINES Filed July 12, 1938 2Sheets-Sheet 2 MEN INVENTOR Theodarfleeg.

WITNESSES:

BY W5 ATTORNEY Patented Nov. 7, 1939 UNITED STATES PATENT OFFHCEIREGULATING SYSTEM FOR GENERATOR DRIVING ENGINES Theodor Deeg,Berlin-Siemensstadt, Germany, assignor to Westinghouse Electric &Manufacturing Company, East Pittsburgh, Pa., a corporation ofPennsylvania Application July 12, 1938, Serial No. 218,751 In GermanyJuly 16, 1937 12 Claims.

My invention relates to electric ship propulsion systems and moreparticularly to a system provided with control means for securingcontinuous stable operation.

Before stating the objects of my invention some explanation of the realproblems involved would be appropriate.

The torque of steam turbines is at zero speed of a turbine and ratedsteam admission (at rated temperature and pressure) substantially equalto twice the turbine torque at rated speed. At approximately twice therated turbine speed the torque would be equal to zero. Between thesethree limits of turbine speed the turbine torque plotted against turbinespeed follows approximately a straight line.

In ship drives, the turbine torque and its power are determined by thecharacteristic of the propeller power plotted against propeller speedand the turbine design, (or the selection of the turbine) is, ingeneral, so made as to correspond or fit to the maximum propeller power,namely, to fit the predetermined maximum propeller speed. Any particularship speed, for mechanical or geared drives, is in general determined bythe adjustment of the steam admission, whereby, as long as a speedincrease or decrease takes place (with different adjustments of steamadmission) up to the rated steam admission, the speed corresponding tothe characteristic of the propeller power is obtained.

With turbo-electric drives of ships it is necessary to utilize agovernor or rotation regulator which, by reason simply of the magnitudeof the rotational speed during reversing of the ship, limits the loadingof the damper windings in the propeller motor. Furthermore, the (ship)reversing operation and the synchronization is simplifled by the use ofa rotation regulator or governor 40 because the driving machine is atall times immediately available to be interconnected and the attendantneed not concern himself with the regulation of the steam admission.After completion of the synchronization the governor speed, or

45 rotation regulator, may, in a simple manner, be used to attain thedesired speed. By adjustment or setting of the speed regulator orgovernor to the desired propeller speed the regulator automaticallyalters the steam admission to the gen- 50 erator driving machine untilthe selected propeller speed is secured. The governor moreover maintainsthis speed always constant regardless of whether the power requirementsrise or fall by reason of changes on the propeller resistance 55 causedby the weather or by effects of changes in water head. The governor hasthe further great advantage of maintaining the rotational speed constantwhen the motor and generator fall out of step and, therefore, offers anextensive reli ability to the generator driving machine.

The size (or design) of the electric drive is determined by the maximum(propeller) torque occurring at full speed of the ship. Certain possibleoperating conditions may, however, lead to torques higher than the ratedtorque and must, therefore, be automatically avoided. Such cases occur,for example, in multi-screw drives when the rudder is moved hard over atfull ship speed or at the loss of a propeller at full ship speed. Inthis case the governor will seek to increase the steam admission of thedriving machine until the selected speed is again attained. At such timethe danger, however, arises that the maximum permissible torque, thepull-out torque, is exceeded. This danger is eliminated in the inventionbecause the governor for the generator driving machine has a device byreason of which the instantaneous maximum permissible torque may not beexceeded. For measuring the maximum permissible torque an electricinstrument is preferably used upon which the actual transmitted torqueand the maximum permissible torque act in an opposite sense. The maximumpermissible torque may, for example, be measured by a wattmeterinstrument, the field of which is influenced by the exciting current ofthe generator and the armature of which is influenced by the excitingcurrent of the motor. The actual transmitted torque may be indicated bya second wattmeter instrument that is so connected to current andpotential transformers of the leads that it is responsive to theexpression EIcos) In this expression E represents generator voltage, 1represents the frequency of the generator voltage, I represents themotor armature current, and the remaining term represents the powerfactor.

For limiting the maximum permissible torque, in the practical embodimentof the invention, a movable stop may, for example, be used which limitsthe steam admission to the driving machine. My control instrument may,of course, be designed so as to operate automatically on the governoradjustment instead of on the position of the stop limiting the openingof the steam admission valve. The instrument may also operate to actuatethe governor adjustment means indirectly,

One broad object of my invention is to maintain stable operation betweena generator and a motor in a power system where the motor is largeenough to take the major portion of the generator load.

Another object of my invention is to so control the operation of a primemover driving a generator that conditions of unstable operation betweenthe generator and a motor coupled to the generator do not arise.

A broad object of my invention in a power system embodying a generator,a prime mover for driving the generator, and a motor is to alter thespeed of the prime mover as a function of the diiierence between thepull-out torque of the motor and the transmitted torque.

A still further object of my invention is to control the turbine speedof a turbo-electric ship propulsion drive as a function of the maximumpermissible torque and the transmitted torque.

The foregoing statements of the objects of my invention are not anexhaustive recitation of objects but merely illustrative. Other objectsand advantages will become more apparent from a study of the followingspecification and the accompanying drawings, in which:

Figure 1 is a schematic showing of an embodimerit of my inventionoperating on the adjustment of the steam admission valve;

Fig. 2 is a schematic showing of my invention in which the control iseffected by operation on the governor adjustment directly; and

Fig. 3 is a schematic fragmentary showing of my invention in which thecontrol is effected by an indirect operation on the governor adjustment.

A regulating device of the first-named type is schematically illustratedin Figure l. A twogear gear-Wheel pump 3, the supply amount of whichvaries as is known approximately proportional to the rotational speed,is driven from the turbine shaft I through a spur gear drive 2. For theconstant outflow cross-section, as, for instance, the fixed opening 6,the supply pressure increases with the rotational speed and, therefore,in proportion to the increased supply of power. This pressure is usedfor rotational speed regulation. The pump supplies fluid flow throughthe space 4 in the opening 5 of one of the pump well shafts and throughthe slot or fixed opening 6 into the open. The governor adjustment may,however, be varied by adjusting the sectional area of opening 6. This isaccomplished by rotation of the cam 4'! to act on the sleeve 48.Further, the liquid pressure arrives through the opening '5 of thesecond pump well shaft in the space 8 and holds the slide bushing 9against the pressure of the spring ii] in equilibrium. Theslide bushing9 covers with its piston parts normally, the channels II and I2 so thatno oil may penetrate from the external oil conductor l3 into thesecanals. The oil conductor I3 is fed by the main constant pressurecontrol oil pump 26 of the turbine set which, at the same time is usedfor the supply of the power means for the movement of the steamadmission valve.

If, for example, the rotational speed of the shaft 9 increases onunloading of the turbine, the oil pressure in space 8 increases anddisplaces the bushing 9 against the spring l0 until a new equilibriumcondition is attained between the oil pressure and the spring force. Atthe same time the pressure 011 is released from the conductor i3 by theentrance of liquid or oil into the canal i i and the oil may penetratefrom there through the hole Hi into the space above the piston it. Atthe same time, the slider bushing 9 opens the exit of the oil from theunderside of the piston iii over the canals l5 and 62 into the open. Theauxiliary piston It moves downward and takes with it the pulling stickif and with it the wedge or cam [8. This wedge at the same timedisplaces the system spring plate is, spring iii and bushing 9 oppositeto the introduced regulating movement until the canals H and ii areagain covered by the bushing ii, and on the occur-- rence of this, theregulating process is brought to rest. The steam admission to theturbine (not shown) is varied by this regulating process through thelevers 2i] and 2| and the controi slider the spring 22 operating a rigidmember (this only holds for the opening process), because its springtension is larger than the small resist-- ance in the stick. In theabove-described process, the downward movement of the pulling stick i!effects an upward movement of the control slider 22 since the lever 21at first has its pivot point on the valve spindle 25 as pivot. As theslider 22 is moved upwardly, pressure oil enters from the conductor isin the upper side of the force piston 24 and simultaneousy the oil fromthe under side of the force piston flows away, so that the steam valve23 of the turbine closes. The valve comes to rest when the spindle 25 isled through the lever ii of the control slider 22 again to the centerposition.

On a decrease of the turbine rotational speed by reason of the loading,the above-described regulating process takes place in the reverse sense.The degree of nonuniformity of the regulator is determined by theselection of the hubs and lever lengths, as well as by the inclinationof the wedge l 8. The construction and the operation of the regulator inaccordance with this description is known.

To limit the maximum permissible moment at any instant, a piston serveswhich adjusts a stop 32 that cooperates with the lever system 2i in suchmanner that the opening of the steam admission valve 23 for the turbineis limited by the stop 32. The piston 3i is controlled by the controlslider 33 which is set through the levers tit, 35 by a regulatinginstrument 3% recording the maximum permissible torque. The regulatinginstrument has two wattmeter systems 3'! and 38 operating opposite toeach other which act on a common shaft 39. The system 31 measures therotational moment transferred from the generator iil to the motor M.This device has a field coil 42 which is connected to a currenttransformer 63 and is excited in proportion with the stator current. Thedeflecting coil M is connected through the choke 45 to the potentialtransformer The potential transferred by the potential transformer isdisplaced in phase byilO" with reference to the operating currentportion of the current. Since the choke coil, if it is very large incomparison to the ohmic impedance of the measuring mechanism, effects adisplacement of the current flowing therethrough of 90, the currentflowing in the frame is in phase with the work current portion of themachine stator current. The measuring mechanism 37 accordingly producesa torque on shaft 39 proportional to E I cos 0 i which isproportionately equal to the transmitted torque.

The maximum permissible torque is dependent on the exciting current ofthe machines operating on each other. This value is measured by thewattmeter system 38, the field winding 51 of which is supplied withcurrent proportional to the generator exciting current and thedeflecting coil 53 of which is supplied with current proportional to themotor exciting current. Accordingly, by this system a torque is producedon shaft proportional to the product of the generator and motor excitingcurrents. By comparing the torques opposite to each other of the twowattmeter systems 38 and 31 with the aid of the common shaft 39, theresulting torque which is present is measured so that, accordingly, thestop it? may, at any time, be so set that the maximum permissiblerotational movement is never exceeded.

The electrical regulating instrument which indicates the deviation fromthe maximum permissible torque may also be permitted to act on thecontrol device in another manner. In Fig. 2, an exemplary embodiment isillustrated in which the instrument 36 influences the outflowcross-section of the gear-wheel and pump 3. The shaft 39 of theinstrument in this arrangement displaces a slider 5i which acts to chokeoff the flow of the control oil into the open. For this purpose thecontrol slider which sets the slot 6 in dependence upon the curve disk4"! of the rotational speed displacement is here arranged in a chamber52 to which an oil conductor 53 leading into the open is connected. Onthe attainment of the maximum permissible rotational moment, the oilconductor it is choked off by the slider 5! so that in this manner aneffect on the control of the steam admission in the sense of alimitation is attained. In the embodiment illustrated in Fig. theseparate stop 32 illustrated in the Fig. l apparatus and the associatedcontrol apparatus Lil, 33 may be omitted.

The regulating instrument which measures the permissible maximumrotational moment may also be permitted to act on the lever which servesfor setting the curved disk 4i and an exemplary embodiment of this isschematically indicated in Fig. 3. Here only the slider 48 of the gearwheel pump 3 is illustrated of the device for the control of the drivingmeans supplied to the turbine. The curved disk 4'5 is displaced with theaid of the levers (5i, (i2, 63, B4, 65, 65. Here 64 identifies a controllever which is displaced in correspondence with the desired governoradjustment that is the desired turbine rotational speed, for example, byhand in the direction of the arrow upwardly or downwardly. On thisdisplacement, the lever 63 rotates about the pivot point 61 fixed by thepiston 88 and correspondingly displaces the ourved disk 41. Theinstrument 36 which measures the maximum permissible rotational speedengages at the right hand end of the lever 66 and displaces this leverupwardly or downwardly in accordance with the measured value, the lever86 also then turning about the point iii. In this displacement of. thelever 55, the control slider 59 is displaced in such a sense that thepiston 68 is lifted or dropped. The consequence of this is that thepivot point Ell of the stick is thrust upwardly or downwardly. On theattainment of the maximum permissible rotational moment, this pivotpoint is so set that the curved disk il is displaced in the sense of adecrease of the rotational speed to the value of the permissible turbinerotational moment.

Obviously, the given limiting device is not limited to the case treatedin the example of a Thoma liquid regulator shown, but may of course beused also in other regulator devices, for example, spring regulators.

I am, of course, aware that others, particularly after having had thebenefit of the teaching of my invention, may devise still other systemsof control falling within the spirit of my invention. I, therefore, wishto be limited only by the scope of. the claims hereto appended and suchprior art as may be pertinent.

I claim as my invention:

1. In a ship propulsion system, in combination, a generator, a motor, aturbine for driving the generator, and means, responsive to the ratio ofthe maximum permissible motor torque to the transmitted torque adaptedto control the steam admission to the turbine.

2. In a turbo-electric ship propulsion system, in combination, aturbine, a generator, having field windings, driven by the turbine; amotor, having field windings, coupled to the propeller to drive thepropeller and connected to the generator to be supplied with electricenergy; and means, responsive to the excitation currents in the fieldwindings of both generator and motor and responsive to the powertransmitted from the generator to the motor, adapted to control thefluid admission to the turbine.

3. In a power system the combination of, a prime mover, means forcontrolling the speed and thus the torque of the prime mover, agenerator coupled to the prime mover, a motor connected to thegenerator, and means, responsive to the ratio of the maximum permissibletorque of the motor and the torque transmitted, adapted to control themeans for controlling the speed of the prime mover.

4. In a power system the combination of, a prime mover, means foraltering the speed of the prime mover, a generator coupled to the primemover to be driven by the prime mover, a motor electrically connected tothe generator, and means, responsive to the ratio of the powertransmitted from the generator to the motor to the product of thefrequency of. the generator and the field currents of the motor andgenerator, adapted to modify the operation of the means for altering thespeed of the prime mover.

5. In an electric power system, including a generator, a variable speedprime mover for operating the generator, a motor connected to thegenerator, of means, jointly responsive to voltage of the generator, thearmature circuit of the motor, the field currents of the motor andgenerator, the speed of the generator and the power factor, adapted toalter the operating characteristic of the prime mover.

6. In a power system including a variable speed prime mover, a generatordriven by the prime mover, a motor electrically connected to be operatedby the generator, means for controlling the speed of the prime mover,and means, jointly responsive to the torque transmitted by the motor andthe maximum permissible torque, adapted to alter the operating effect ofthe means for controlling the speed of the prime mover.

7. In a power system including a variable speed prime mover, a generatordriven by the prime mover, a motor electrically connected to be operatedby the generator, and means responsive to a predetermined change in thedifference between the pull-out torque of the motor and the actualtorque transmitted by the motor adapted to alter the speed of the primemover.

8. In a turbo-electric ship propulsion system, in combination, aturbine, a governor for the turbine adapted to maintain the turbinespeed constant, governor adjusting means adapted to select the speed atwhich the turbine is to operate, a generator driven by the turbine, amotor connected to the generator adapted to drive the ship propeller,means responsive to the pull-out torque of the motor, means responsiveto the torque transmitted by the motor, and means responsive to thedifferential effect of said last two means adapted to change theadjustment of the governor adjusting means.

9. In a turbo-electric ship propulsion system, in combination, aturbine, a governor for the turbine adapted to maintain the turbinespeed constant, governor adjusting means adapted to select the speed atwhich the turbine is to operate, a generator driven by the turbine, amotor connected to the generator adapted to drive the ship propeller,means responsive to the pull-out torque of the motor, means responsiveto the torque transmitted by the motor, and means responsive to thedifierential efiect of said last two means adapted to jointly with saidgovernor control the speed of the turbine.

10. In a turbo-electric ship propulsion system, in combination, aturbine, a governor for the turbine adapted to maintain the turbinespeed constant, governor adjusting means adapted to select the speed atwhich the turbine is to operate, means for varying the turbine speed inspite'oi' the governor operation, a generator driven by the turbine, amotor connected to the generator adapted to drive the ship propeller,means responsive to the pull-out torque of the motor, means responsiveto the torque transmitted by the motor, and means responsive to thediflerential eifect of said last two means adapted to operate said speedvarying means.

11. In a turbo-electric ship propulsion system, in combination, aturbine, a governor for the turbine adapted to maintain the turbinespeed constant, governor adjusting means adapted to select the speed atwhich the turbine is to operate, means for varying the turbine speed inspite of the governor operation, a generator driven by the turbine, amotor connected to the generator adapted to drive the ship propeller,means responsive to the pull-out torque of the motor, means responsiveto the torque transmitted by the motor and means responsive to thediiferential effect of said last two means adapted to control theoperation of the speed varying means whereby the governor and speedvarying means jointly alter the speed of the turbine.

12. In a ship propulsion system, in combination, an engine, means forvarying the speed of the engine, a generator coupled to the engine, amotor coupled to the propeller, means responsive to the torquetransmitted by the motor, means responsive to the pull-out torque of themotor, and means responsive to the differential effect of said last twomeans adapted to vary the speed of said engine.

THEODOR DEEG.

